Talk like an architect

4D printing – creating materials that can transform their shape in response to changes in their environment

Adaptive façade – a façade that can change to maximise a building’s energy efficiency and comfort of its occupants, for example by using shading systems

Biomimetic – designed and engineered to mimic a natural system

Façade – the exterior of a building

Shading system – a mechanical system that uses moving panels to cover a building’s windows to prevent overheating and excessive brightness inside when it is sunny

Thermal equilibrium – a state where heat entering and leaving a system is balanced, so the temperature remains constant

When the weather is cold, heating keeps our buildings warm. When the temperature outside rises, we use air conditioning to cool them down. However, these systems use huge amounts of energy (often provided by fossil fuels) and even then, we can still find ourselves sweating in summer or shivering our way through winter.

To make buildings more energy efficient and comfortable for their occupants, architecture researcher Dr Negin Imani from Bodeker Scientific is taking inspiration from nature. Since 2021, she has spearheaded nationally significant research on biomimetic adaptive building façades for energy efficiency, through two prestigious projects funded by the New Zealand Ministry of Business, Innovation and Employment. “An adaptive façade is a building ‘skin’ that can change depending on how much sun there is, or how hot or humid it is,” she explains. “This reduces the need for heating, cooling and artificial lighting inside, making buildings more comfortable and efficient.”

“We can learn from biological systems and apply natural ideas to buildings,” Negin continues. “It’s not about copying how something looks but understanding how it works and translating that logic into building design.”

Learning from leaves

“The inspiration for our biomimetic adaptive façade came from how plants use stomata to regulate heat and moisture,” says Negin. Plant leaves are covered in tiny holes called stomata which open and close to regulate heat, moisture and gas exchange. Their behaviour is governed by changes in environmental conditions such as temperature and humidity. Stomata tend to open during the day to let in carbon dioxide for photosynthesis, then close at night to preserve water. However, during drought conditions, stomata close to reduce water loss and prevent dehydration. In more humid conditions, they remain open as the risk of water loss is reduced, allowing for continued gas exchange. Negin and her multidisciplinary, multi-institution team are designing biomimetic adaptive façades that respond to environmental conditions, inspired by plant stomata.

Buildings with balance

Negin has designed a shading system for an adaptive façade that includes both active and passive components. “Active systems depend on an external energy input (typically electricity) to move and use sensors, motors and control systems to respond dynamically to environmental conditions,” she explains. “They are very precise and responsive but can be complex and require ongoing maintenance.” In the motorised component of Negin’s shading system, rotating panels are controlled by artificial intelligence (AI) to adjust the amount of sunlight hitting a building’s windows, thereby altering the temperature and brightness inside to maintain maximum comfort and energy efficiency.

In contrast, passive systems do not need external energy input so are more energy efficient. They are made from materials that self-regulate by changing shape or properties in response to temperature, light levels or moisture in the atmosphere. “These materials can now be programmed through their composition, structure and fabrication process to behave in specific ways,” says Negin. She uses 4D printing to create materials that react to moisture, and has incorporated these into her shading system so that it also automatically responds to changes in humidity.

Intelligent designs

By combining an active motorised system with a passive shape-changing material, Negin has designed a shading system for an adaptive façade that responds to environmental conditions. “The active system, especially when supported by AI, gives control, precision and the ability to adapt the façade in real time, while the passive system provides an energy-free response,” she says. “Together, they create a smarter, more efficient and more responsive adaptive façade.”